In general, the present invention relates to a communication system, more particularly, relates to a communication system that allows the communication to be switched to the so-called television telephone with ease during a telephone conversation dependent on the voice of the conversation partner.
An ordinary telephone set only allows a voice telephone conversation with a partner. With a television-telephone set, however, the user can have a telephone conversation with a partner looking at an image of the partner. In addition, by connecting a video camera to a personal computer, the user can also have a telephone conversation with a partner through the Internet looking at an image of the partner as is the case with a television-telephone set.
In order to have a telephone conversation with a partner while looking at an image of the partner by using a television-telephone set or to have a telephone conversation with a partner through the Internet looking at an image of the partner by connecting a video camera to a personal computer, however, it is necessary for the user to be present in a particular room, a fixed place or the like where the television-telephone set or the personal computer is placed. That is to say, there is a problem that the user is not capable of having a telephone conversation with a partner while looking at an image of the partner with ease when the user is not present at the particular room or he is out.
As a possible solution to the problem described above, that is, in order to make the television telephone usable at any place, the function of a portable telephone device which is widely used at the present time is extended so that the portable telephone device may be functioning as a television-telephone set.
In this case, however, it is necessary to incorporate components such as a CCD camera, a liquid crystal display device and an image compressing/decompressing circuit in the body of the portable telephone device itself. As a result, the portability inherent in the portable telephone device is lost substantially due to causes such as an increase in device size, an increase in device weight and a decrease in battery life.
In stores selling home electrical appliances, on the another hand, a large number of television receivers and VTRs of the integrated-camera type are displayed and there is adopted an exhibition technique of displaying images of customers visiting the stores taken by cameras and broadcasted television programs by the television receivers all the time. If the equipments for taking and displaying these images can be combined with the portable telephone device carried by the user, to implement a television-telephone set, the user is able to use a television-telephone set at any place by only visiting for example any of stores selling home electrical appliances which exist in a wide region without losing the portability of the potable telephone device itself.